![]() Colombara, Diego ![]() in Scientific Reports (2017), 7 Alkali metal doping is essential to achieve highly efficient energy conversion in Cu(In,Ga)Se2 (CIGSe) solar cells. Doping is normally achieved through solid state reactions, but recent observations of ... [more ▼] Alkali metal doping is essential to achieve highly efficient energy conversion in Cu(In,Ga)Se2 (CIGSe) solar cells. Doping is normally achieved through solid state reactions, but recent observations of gas phase alkali transport in the kesterite sulfide (Cu2ZnSnS4) system (re)open the way to a novel gas-phase doping strategy. However, the current understanding of gas-phase alkali transport is very limited. This work (i) shows that CIGSe device efficiency can be improved from 2% to 8% by gas-phase sodium incorporation alone, (ii) identifies the most likely routes for gas-phase alkali transport based on mass spectrometric studies, (iii) provides thermochemical computations to rationalize the observations and (iv) critically discusses the subject literature with the aim to better understand the chemical basis of the phenomenon. These results suggest that accidental alkali metal doping occurs all the time, that a controlled vapor pressure of alkali metal could be applied during growth to dope the semiconductor, and that it may have to be accounted for during the currently used solid state doping routes. It is concluded that alkali gas-phase transport occurs through a plurality of routes and cannot be attributed to one single source. [less ▲] Detailed reference viewed: 306 (14 UL)![]() Spindler, Conrad ![]() ![]() ![]() in Applied Physics Letters (2016), 109 Detailed reference viewed: 246 (25 UL)![]() Siebentritt, Susanne ![]() ![]() ![]() in Solar Energy Materials and Solar Cells (2015) Detailed reference viewed: 272 (8 UL)![]() Meadows, Helen ![]() ![]() ![]() Scientific Conference (2015) Detailed reference viewed: 242 (4 UL)![]() Colombara, Diego ![]() ![]() ![]() in Electrochemistry Communications (2014), 48 The quality control of individual semiconductor thin films during fabrication of multiple layers is important for industry and academia. The ultimate aim of this research is to predict the efficiency of p ... [more ▼] The quality control of individual semiconductor thin films during fabrication of multiple layers is important for industry and academia. The ultimate aim of this research is to predict the efficiency of p-–n junction solar cells by photoelectrochemical analysis of the bare p-type semiconductor. A linear correlation between the photocurrent measured electrochemically on Cu(In,Ga)Se2 absorber layers through a Eu3+ electrolyte junction and short circuit current and efficiency of the corresponding solid state devices is found. However, the correlation is complicated by pronounced recombination at the semiconductor/electrolyte interface, while the solid state interface behaves more ideally. [less ▲] Detailed reference viewed: 229 (9 UL)![]() Regesch, David ![]() Doctoral thesis (2014) The quasi-Fermi level splitting (qFls) in a solar cell absorber limits the maximum achievable open circuit voltage of the final device. A calibrated photoluminescence set-up allows the determination of ... [more ▼] The quasi-Fermi level splitting (qFls) in a solar cell absorber limits the maximum achievable open circuit voltage of the final device. A calibrated photoluminescence set-up allows the determination of the qFls at room temperature under conditions equivalent to the illumination from the sun. In this work the qFls is used as an indicator for the quality of epitaxial and polycrystalline thin CuInSe2 films with different compositions. It is shown, that the epitaxial material exhibits improved optoelectronic quality noticeable in the higher qFls (50-100meV) when compared to the polycrystalline counterpart. Furthermore, a dependency on the Cu/In ratio is noticed: In Cu poor material (Cu/In<1) the qFls increases with an increasing Cu concentration and levels off for the absorbers grown under Cu-rich conditions (Cu/In>1). The difference between absorbers grown under Cu-poor and Cu-rich conditions is found to be in the order of 150meV. Additionally, the compositional dependence of the Urbach energy and of the band gap energy has been evaluated from the PL spectra at room temperature. Slightly higher bandgaps and lower Urbach energies have been found for the Cu rich material compared to the Cu poor absorbers. The time dependent change of the qFls of bare CuInSe2 absorbers exposed to air is presented and shows for Cu-poor absorbers a pronounced and for Cu-rich material a slower degradation. It is shown, that a chemical etching in potassium cyanide refreshes the degraded material to an extent comparable to freshly grown samples, and that the deposition of a CdS buffer layer passivates the surface. Epitaxial Cu(In,Ga)Se2 is grown by means of metal organic vapour phase epitaxy and used to produce epitaxial solar cells. A maximum power conversion efficiency of 6.7% has been achieved. All solar cells suffer from dominant interface recombination processes which limit the device performance. The critical interface is between the absorber layer and the CdS buffer and related to the high gallium content. [less ▲] Detailed reference viewed: 274 (38 UL)![]() Weiss, Thomas ![]() ![]() ![]() in IEEE JOURNAL OF PHOTOVOLTAICS (2014), 4 Detailed reference viewed: 205 (12 UL)![]() Meadows, Helen ![]() ![]() in Journal of Physical Chemistry. C, Nanomaterials and interfaces (2014), 118 (3) Detailed reference viewed: 221 (13 UL)![]() Malaquias, Joao Corujo Branco ![]() ![]() ![]() in Physical Chemistry Chemical Physics (2014), 16 Detailed reference viewed: 170 (8 UL)![]() Redinger, Alex ![]() ![]() in Thin Solid Films (2014) Detailed reference viewed: 200 (8 UL)![]() Meadows, Helen ![]() ![]() ![]() in Thin Solid Films (2014) Detailed reference viewed: 155 (2 UL)![]() Depredurand, Valérie ![]() ![]() ![]() in Applied Physics Letters (2014), 105 Detailed reference viewed: 183 (11 UL)![]() ; Larsen, Jes K. ![]() in Solar Energy Materials and Solar Cells (2014), 126 Detailed reference viewed: 205 (9 UL)![]() Siebentritt, Susanne ![]() ![]() ![]() in Solar Energy Materials and Solar Cells (2013) Detailed reference viewed: 236 (5 UL)![]() Regesch, David ![]() ![]() ![]() in Applied Physics Letters (2012), 101 Detailed reference viewed: 213 (10 UL)![]() Gutay, Levent ![]() ![]() ![]() in Physical Review (2012), 86 Detailed reference viewed: 233 (10 UL)![]() Gütay, Levent ![]() ![]() ![]() in Applied Physics Letters (2011), 99(151912), 1519121-15191123 Detailed reference viewed: 127 (17 UL) |
||